During this research project, I want to delineate ultrastructural morphology of bone as an organ and as a tissue in humans and animals during normal growth, development, and aging and to describe variations of normal growth produced by experiment and disease. I will correlate these studies with light microscopic and biochemical examination of the same tissues. This includes examination of nerve supply of bone as a function of age; determination of the type of nerve endings in bone; examination of ligament and tendon insertions as related to age, experiment, and disease; examination of epiphyseal and epiphyseal plate development in normal animals and humans, and during epiphyseal growth and developmental disorders. I want to determine microscopic, ultrastructural, electrical and mechanical changes in cat skeletal muscle during disuse and denervation atrophy and during regeneration after disuse. I want to compare these findings with biopsies of human neuromuscular disease. I hope also to delineate the normal ultrastructural morphology of muscle spindles.